New feature: Class-based scopes backends. Listing scopes, available scopes and default scopes
is now done through the class that the SCOPES_BACKEND_CLASS setting points to.
By default, this is set to oauth2_provider.scopes.SettingsScopes which implements the
legacy settings-based scope behaviour. No changes are necessary.

Dropped support for Python 3.2 and Python 3.3, added support for Python 3.6

Support for the scopes query parameter, deprecated in 0.6.1, has been dropped

#448: Added support for customizing applications’ allowed grant types

#141: The is_usable(request) method on the Application model can be overridden to dynamically
enable or disable applications.